How to add labels into Chart.js canvas plugin?

Question

I'm using the awesome plugin Chart.js, and I'm trying to find the way of display labels within each percentage. So I googled it, and I found this pull: https://github.com/nnnick/Chart.js/pull/35

I did a simple fiddle to test it, but doesn't works: http://jsfiddle.net/marianico2/7ktug/1/

This is the content:

HTML

<canvas id="canvas" height="450" width="450"></canvas>

JS

$(document).ready(function () {
    var pieData = [{
        value: 30,
        color: "#F38630",
        label: 'HELLO',
        labelColor: 'black',
        labelFontSize: '16'
    }, {
        value: 50,
        color: "#E0E4CC"
    }, {
        value: 100,
        color: "#69D2E7"
    }];

    var myPie = new Chart(document.getElementById("canvas").getContext("2d")).Pie(pieData, {
        labelAlign: 'center'
    });
});

---

I'm afraid there is no information about this in the documentation.

Also I'd like to know how to display a label for each portion, but outside the chart. Linked by a line. As do the charts of highcharts.js.

By the way, I'd be glad if you recommend me an html5 chart alternative which includes the options I said above. I've heard about the flot plugin, but I'm afraid does not support animations...

If you need more info, let me know and I'll edit the post.

Answer 1

You'll have to add code in 2 places. As an example, take the doughnut. First add label info to the defaults (look at the original Chart.js code and compare with this):

    chart.Doughnut.defaults = {
        segmentShowStroke : true,
        segmentStrokeColor : "#fff",
        segmentStrokeWidth : 2,
        percentageInnerCutout : 50,
        animation : true,
        animationSteps : 100,
        animationEasing : "easeOutBounce",
        animateRotate : true,
        animateScale : false,
        onAnimationComplete : null,
        labelFontFamily : "Arial",
        labelFontStyle : "normal",
        labelFontSize : 24,
        labelFontColor : "#666"
    };

Then go down to where the Doughnut is drawn and add the four ctx lines.

    animationLoop(config,null,drawPieSegments,ctx);

    function drawPieSegments (animationDecimal){
        ctx.font = config.labelFontStyle + " " + config.labelFontSize+"px " + config.labelFontFamily;
        ctx.fillStyle = 'black';
        ctx.textBaseline = 'middle';
        ctx.fillText(data[0].value + "%", width/2 - 20, width/2, 200);

The ctx.fillText call will put the text onto the canvas, so you can use that to write text with x,y coordinates. You ought to be able to use this way to do basic labels. Here is the jsfiddle to tinker with:

http://jsfiddle.net/nCFGL/ (look at lines 281 and 772 in the JavaScript section of the jsfiddle for aforementioned code)

If you need something fancier, someone forked a version of Charts.js and added tooltips. Here is the discussion https://github.com/nnnick/Chart.js/pull/35, and you'll be able to find the link to the forked version inside that discussion.